Kingswood Software Development Tools AS80
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NAME
as80 - assembler for 8080, 8085 and Z80 microprocessors.
SYNOPSIS
as80 [-gchlnopqstvwxz] file
DESCRIPTION
This documentation is for as80 [1.07].
Copyright 1990-1994, Frank A. Vorstenbosch, Kingswood Software.
AS80 is an assembler for the Intel 8080/8085 and Zilog Z80
microprocessors. It reads input from an ASCII text file, assembles
this into memory, and then writes a listing and a binary or hex file.
AS80 is case sensitive, not only does it differentiate between the
labels XYZ and xyz, but it also requires all (pseudo) instruction and
register names to be lower case. This way, the listing is the most
readable. Option -i can be used to make the assembler case insensitive.
Alternatively, the included TOLOWER program can be used to convert
sources to lower case.
OPTIONS
As80 recognizes the following options:
-c Show number of cycles per instruction in listing. This
decreases the number of columns available for listing by 5.
The number of cycles is printed between brackets [ and ].
-g Generate source-level debug information file. This file
can then be used in in-system debugging or a software
simulator.
-h
Specify height of page for listing. This option determines
the number of lines per printed page. Each page has a header
and is terminated by a form-feed character. The special
case -h0 indicates an infinite page length. In this case,
page breaks are only inserted between the two passes and
the symbol table (if present).
-i Ignore case in opcodes. In this way, the assembler does not
differentiate between 'add' and 'ADD', for example. Labels
are still case sensitive.
-l Generate pass 2 listing.
-l
Listing file name. The listing file is used for pass 1 and
pass 2 listing, for the symbol table (printed between the
two passes), and some statistics. When neither -p nor -t
is specified, and -l is given, then the assembler
automatically generates a pass 2 listing. When -p or -t is
specified, an additional -l should be given is a pass 2
listing is required. The filename - can be used to direct
the listing to standard output.
-l Generate pass 2 listing.
-n Disable optimizations. When this option is specified no
optimizations will be done, even when the OPT pseudo-
instruction is used in the source code.
-o
Specify binary or s-records output file name. The assembler
automatically adds ".bin" for binary output or ".s19" for
s-records output when no extension is given.
-p Generate pass 1 listing. This may be used to examine any
optimizations/bugs generated in pass 2.
-q Quiet mode. No running line counter is displayed on standard
error output.
-s Write s-records instead of binary file. The s-records file
contains data for (only) the used memory; the binary file
begins at the lowest used address, and continues up to the
highest used address; filling unused memory between these
two addresses with either $ff or $00.
-s2 Write intel-hex file instead of binary file. The intel-hex
file contains data for (only) the used memory.
-t Generate symbol table. The symbol table is listed between
passes one and two, displaying the name, hexadecimal and
decimal value of each label, using 4-digit hexadecimal
numbers where possible, otherwise 8-digit numbers. The
decimal value is followed by an asterisk if the label is
redefinable (defined using SET instead of EQU).
-v Verbose mode. More information is displayed on standard
output.
-w
Specify column width. Normally, the listing is printed using
79 columns for output to a 80-column screen or printer. If
the -w option is given without a number following it, then
the listing will be 131 columns wide, otherwise it will be
the number of colulmns specified (between 60 and 200).
-x1 Use 8085 extensions. The 8085 CPU has two additional
instructions and different cycle counts, but is otherwise
software compatible to the 8080. When this option is not
specified the assembler rejects the RIM and SIM instructions.
-x or
-x2
Use Z80 extensions. The Z80 has many additional instructions
and addressing modes, but is otherwise software compatible to
the 8080. When this option is not specified the assembler
rejects all Z80 new instructions and addressing modes.
-x3 Use Z80 extensions and index register byte instructions.
The IX and IY registers were originally intended to be
split in IXH/IXL and IYH/IYL register pairs. For some
reason (bug in original mask set?) these instructions were
not included by Zilog in the programming manuals, but
they do work on all CPUs I've seen. Your mileage may vary.
Note that these extensions do NOT work on the Z180/181 and
H64180, but they DO (and are documented) on the Z280.
-z Fill unused memory with zeros. Normally when a binary file
is generated, unused bytes between the lowest and highest
used addresses are filled with $ff, the unprogrammed state
of EPROMs. If this is not wanted, the -z option can be used
to initialize this memory to $00. With s-records, unused
memory is not output to the file, and this option forces the
creation of an S9 (start address) record instead, even if no
start address is specified in the file with the END pseudo-
instruction.
Commandline options can be catenated, but no other option can follow
one that may have a parameter. Thus:
-tlfile
is correct (specifying symbol table and pass 2 listing), but
-h5t
is not.
It is possible to discard any of the the output files by specifying
the name 'nul'.
EXPRESSIONS
The assembler recognizes most C-language expressions. The operators
are listed here in order of precedence, highest first:
() braces to group subexpressions
* $ current location counter
unary + - ! ~ unary + (no-operation), negation, logical NOT,
binary NOT
* / % multiplication, division, modulo
+ - addition, subtraction
<< >> shift left, shift right
< > <= >= comparison for greater/less than
= != comparison for equality (== can be used for =)
& binary AND
^ binary XOR
| binary OR
The logical NOT (!) evaluates to zero if the parameter is nonzero,
and vice versa. The binary NOT (~) complements all the bits in its
parameter.
Note: the asterisk is both used as the multiplication operator, and
as symbol for the current location. The assembler determines from
the context which is which. Thus:
5**
is a valid expression, evaluating to five times the current location
counter, and:
2+*/2
is too, evaluating to the current location counter divided by two, to
which two is added. In the same way, the % sign is both used as the
modulo operator and the prefix for binary numbers.
Numbers can be specified in any number base between 2 and 36.
Decimal numbers can be used without a prefix, hexadecimal numbers
can be prefixed by $, octal numbers by @, and binary numbers by %.
Other number bases can be used by using the following format:
#,
where the base is the number base to use (must be specified in
decimal), and number is the value. Thus:
1000 - decimal number, value 10*10*10=1000
%1000 - binary number, value 2*2*2=8
@1000 - octal number, value 8*8*8=512
$1000 - hexadecimal number, value 16*16*16=4096
#1000 - hexadecimal number, value 16*16*16=4096
2#1000 - binary number, value 2*2*2=8
4#1000 - base-4 number, value 4*4*4=64
7#1000 - base-7 number, value 7*7*7=343
36#1000 - base-36 number, value 36*36*36=444528
For number bases greater than 10, additional digits are represented
by letters, starting from A. Both lower and upper case letters can
be used.
11#aa = 120
16#ff = 255
25#oo = 624
36#zz = 1295
PSEUDO-INSTRUCTIONS
align
Align fills zero or more bytes with zeros until the new address
modulo equals zero. If the expression is not present,
align fills zero or one bytes with zeros until the new address
is even.
Example 1:
align 256 ; continue assembly on the
; next 256-byte page
Example 2:
align ; make sure table begins
Table dw 1,2,3 ; on an even address
bss
Put all following data in the bss segment. Only data pseudo-instructions
can be used in the bss segment, and these only increment the location
counter. It is up to the programmer to initialize the bss segment. The
bss segment is especially meaningful in a ROM based system where
variables must be placed in RAM, and RAM is not automatically initialized.
The assembler internally maintains three separate location counters,
one for the code segment, one for the data segment and one for the
uninitialized data segment. The user is responsible for not overlapping
the segments by setting appropriate origins. The code, data and bss
pseudo-instructions can be used to interleave code and data in the source
listing, while separating the three in the generated program. The
assembler starts with the code segment if none is specified.
Example:
code
org $f000 ; Assuming 4 kbyte code ROM
data ; with 2 kbyte program and
org $f800 ; 2 kbyte initialized data
bss
org 0 ; bss segment is in RAM
Buffer ds 100
code
Begin ld hl,Table
ld de,Buffer
ld bc,3
ldir
.
.
.
data
Table db 1,2,3
code
MyFunc ld ix,Table
.
.
code
Put all following assembled instructions and data in the code segment.
See BSS.
data
Put all following assembled instructions and data in the data segment.
See BSS.
db
Define bytes. The bytes may be specified as expressions or strings,
and are placed in the current (code or data) segment. This pseudo
instruction is similar to the Zilog-defined defb and defm pseudo-
instructions.
Example:
Message db 7,"Error",13,10,0
defb
Define bytes. The bytes may be specified only as expressions,
and are placed in the current (code or data) segment. This
pseudo-instruction is similar to the db pseudo-instruction.
Example:
Message defb 7
defm "Error"
defb 13,10,0
defm
Define message. The bytes may be specified only as a string, and
are placed in the current (code or data) segment. This pseudo-
instruction is similar to the db pseudo-instruction.
ds
defs
Define zero or more bytes empty space. The specified number of
bytes are filled with zeros. This pseudo-instruction is identical
to the Zilog-defined pseudo-instruction defs.
Example:
ds 100 ; reserve 100 bytes here
dw
defw
Define words. The words are placed in the current (code or data)
segment. This pseudo-instruction is identical to the Zilog-
defined defw pseudo-instruction.
Example:
ld a,Function ; number of function
ld hl,JumpTable
add a,a
add a,l
ld l,a
adc a,h
sub l
ld h,a
jp (hl) ; jump to function
JumpTable dw Function0
dw Function1
dw Function2
else
The else pseudo-instruction can be used for if-then-else
constructions. It must be placed between an if and an endif
instruction. For an example, see the if pseudo-instruction.
end
The end pseudo-instruction is optional, and need not be used. If
it is used, its optional operand specifies the staring address of
the program. This address is displayed when the program is
assembled, and is also placed in the s-record output file.
Example:
end Start
endif
The endif pseudo-instruction must be used to close an if-endif
or if-else-endif construction. For an example, see the if
pseudo-instruction.
equ
The equ (equate) pseudo-instruction sets the specified label to
the value of the expression. The label may not already exist.
Some programmers choose to use only upper-case identifiers for
labels defined in this way to differentiate them from addresses.
Example:
ESCAPE equ 27
if
The if pseudo-instruction can be used in conjunction with the
endif and possibly the else pseudo-instructions to selectively
enable and disable pieces of code in the source. If the expression
given evaluates to zero, then the following code up to the matching
else or endif is not included in the assembly. If the expression
is nonzero, then the following code is included, but any code
between the matching else and endif is not.
The original Zilog assemblers called this pseudo-instruction COND.
Example:
if COUNT=2 | COUNT=4
add a,a ; shift left for counts
if COUNT=4 ; of 2 and 4
add a,a
endif
else
ld b,COUNT ; otherwise use slow multiply
call Multiply
endif
include
The named file is included in the assembly at this point. After
it has been read, assembly continues with the next line of the
current file. Include files may be nested.
Example:
include "defines.i"
list
Enable generation of the listing in the list-file. If the listing
has been disabled twice, it must be enabled twice before it is
generated. When no -p or -l option has been specified on the
command line, this pseudo-instruction has no effect.
nolist
Disable generation of the listing in the list-file.
noopt
Disable optimizations. If the -n option has been specified on the
command line, this pseudo-instruction has no effect.
nop
No operation. When the optional expression is not present, this
is simply the nop instruction of the processor. When the
expression is present, the specified number of nop instructions
are inserted.
Example:
nop 10
opt
Enable optimizations. If the -n option has been specified on the
command line, this pseudo-instruction has no effect.
When optimization is enabled, the assembler tries to use the
shortest and fastest instructions possible which have the effect
the user wants. It may replace any extended-address instruction
by direct-address instructions (provided the direct pseudo-
instruction has been used). It replaces long branches with jumps
or short branches, calls with branches to subroutines, and
replaces zero-offset indexed instructions by no-offset indexed
instructions. The effects of optimizations is clearly visible if
both a pass one and a pass two listing is generated.
org
The org (origin) pseudo-instruction specifies the next address to
be used for assembly. When no origin has been specified, the
assembler uses the value 0. The assembler maintains three separate
location counters: one for the code segment, one for the data
segment, and one for the bss segment. See the code and pseudo-
instruction for more information.
page
When the optional expression is not present, the assembly listing
is continued on the next page. When the expression is present,
the listing is continued on the next page only if the specified
number of lines do not fit on the current page.
set =
The set pseudo-instruction sets the specified label to the value
of the expression. The label may or may not already exist.
Some programmers choose to use only upper-case identifiers for
labels defined in this way to differentiate them from addresses.
Example:
CURRENT set 0
.
.
.
CURRENT set CURRENT+1
struct
struct ,
The struct (structure) pseudo-instruction can be used to define
data structures in memory more easily.
The name of the structure is set to the total size of the structure;
if the expression is present, the starting offset is the value of
the expression in stead of zero.
Between the struct and end struct pseudo-instructions the following
pseudo-instructions can be used: db, dw, ds, label, align.
Within structures these pseudo-instructions take a slightly different
format than normally:
db element is one byte
dw element is two bytes
ds , element is the specified number of bytes
ds skip the specified number of bytes
label element is zero bytes, i.e. set the name
to the current structure offset
align skip until (offset%expression)=0
align skip until offset is even
Example:
struct ListNode,4
dw LN_Next
dw LN_Previous
db LN_Type
align
label LN_Simple ; size of structure so far
align 8
ds LN_Data,10
end struct
This is identical to:
LN_Next equ 4 ;\
LN_Previous equ 6 ; offset of structure elements
LN_Type equ 8 ;/
LN_Simple equ 10 ; size of structure so far
LN_Data equ 16 ; offset of structure element
ListNode equ 26 ; size of structure
title
The title pseudo-instruction sets the title to be used in the
header of each listing page. The string should be no longer than
80 characters.
Example:
title "DIS80 : A disassembler for a 8080 CPU"
ADDRESSING MODES
The assembler allows all 8080 (and when enabled also Z80) addressing
modes. The use of an expression between braces as an address disallows
braces at the outermost level for immediate values. The assembler
is capable to determine that
ld a,(10)+1
and
ld a,1+(10)
are immediate operands. You can also use rectangular brackets
[ and ] to include an address.
List of available modes:
immediate
(address)
(bc) (de) (hl) (sp)
Additional addressing modes for the Z80:
(ix+offset) (ix-offset)
(iy+offset) (iy-offset)
(c)
LIST OF ACCEPTED INSTRUCTIONS
adc add align and bit bss call ccf code cp cpd cpdr cpi cpir cpl daa
data db dd dec defb defm defs defw di disable djnz ds dw ei else enable
end endif equ ex exx fcb fcc fcw fdb halt if im in inc include ind indr
ini inir jp jr ld ldd lddr ldi ldir list neg nolist noopt nop opt or
org otdr otir out outd outi page pop push res ret reti retn rim rl rla
rlc rlca rld rmb rr rra rrc rrca rrd rst sbc scf set shl shr sim sl sla
sr sra srl stc struct sub title tsti xor
Of these instructions, the following are (more or less) synonymous,
and can be used interchangably.
YOU CAN USE WHERE YOU WOULD PREVIOUSLY USE
nop 6 - nop nop nop ....
push bc,de - push bc ; push de
pop bc,de - pop de ; pop bc (note reversed order)
disable - di
enable - ei
sr - srl
shr - srl
sl - sla
shl - sla
stc - scf
ld bc,de - ld b,d ; ld c,e
ld ix,bc - ld xh,b ; ld xl,c
add R - add a,R
or a,R - or R
in (c) - tsti (c)
ex hl,de - ex de,hl
djnz LBL - dec b ; jp nz,LBL
jp nv,LBL - jp pe,LBL (no overflow/parity even)
jp v,LBL - jp po,LBL (overflow/parity odd)
jp ns,LBL - jp p,LBL (no sign/positive)
jp s,LBL - jp m,LBL (sign/negative)
Operands:
xh - ixh
xl - ixl
yh - iyh
yl - iyl
[Address] - (Address)
[hl] - (hl)
(ix-6) - (ix+-6)
And pseudo-instructions:
db - defb, defm
dw - defw
ds - defs
= - set
struct - lots of EQUs
LIST OF OTHER KEYWORDS
! != $ % & ( ) * + , - / < << <= = > >= >> [ ] ^ | ~
a af af' align b bc c d db de ds dw e end h hl i ix ixh ixl iy iyh
iyl l label m nc ns nv nz p pe po r s sp struct v xh xl yh yl z
FILES
.a80 - source file.
.z80 - source file -- first alternative.
.asm - source file -- second alternative.
.lst - List file.
.s19 - Motorola S-records output file.
.hex - Intel hex output file.
.bin - Binary output file.
BUGS
No provision for linking other pre-assembled modules is made.
RETURNS
As80 returns one of the following values:
0 - Source file assembled without errors.
1 - Incorrect parameter specified on the commandline.
2 - Unable to open input or output file.
3 - Assembly gave errors.
4 - No memory could be allocated.
DIAGNOSTICS
Help message if only parameter is a question mark, or if an
illegal option has been specified.
AUTHOR
This is copyrighted software, but may be distributed freely as long
as this document accompanies the assembler, and no copyright messages
are removed. You are explicitly NOT allowed to sell this software
for anything more than a reasonable copying fee, say US$5.
To contact the author:
Frank A. Vorstenbosch
Kingswood Software
P.O. Box 85800 Phone: +31-(70)-355 5241
2508CM The Hague BBS: +31-(70)-355 8674
Netherlands Email: prompt@xs4all.nl
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